What did you do to your CJ today?

Had to fix my fuel sender as my gauge would only go between full and just above half tank. It is on a CJ7 with Mopar MPI kit with modified fuel sender to also hold an in tank fuel pump. Started out pretty straight forward, pulled out the sender/fuel pump assembly, measured sender ohs and saw it would not move beyond ~25ohm. No spare unit so I opened up the sender housing and saw the issue. The cheap Chinese sender used as the base for the modified fuel pump assembly had a bent phenolic board that held the resistance wire. Pulled it out and it flexed back. The phenolic board was just too thin. Crammed in a piece of chemical resistant rubber mat and viola, the sender workd fine. Put everything back together and remounted the tank.

Turned on the ignition and the fuel guage read properly, yay - until I went to start the jeep. Crank, no start Solid CEL illuminated. sigh! hooked up the scanner, no joy - no comms to the computer. Pulled out the diagnostic scanner and same thing. Computer totally unresponsive. Ugh. Pulled out a spare computer and same issue - ok computer probably OK, must be some kind of power problem. Check all the fuses I could find and all looked good. Had to stop for the night as no more sun and kids needed to eat.

Searched all night googling MPI Kit schematic/wiring diagrams to no joy. Looked through my JY schematics and figured something was going on in the ASD circuit, so collected some data and printed it out for later work.

Got back into it this afternoon, dropped the tank again, checked the sender, ok, checked the fuel pump and the power supply pin was shorted to ground. Had to pull sender back out and figure out what happened. Turns out the sender mod for the fuel pump di not have the correct type of hole centering washer to prevent the power post from shorting out. tracked one down and fixed the sender up and put it all back together. Not installing the tank this time. Powered the CJ back up and still no computer comms or start, just crank. Pulled the computer connector off and measured the Battery pin and no power. Definitely something dead on the ASD circuit. The MPI Kit instructions did not seem to have anything about a fuse or I missed it, however the YJ schematics stated the ASD power feed is fused. Traced the power for the ASD relay and sure enough there was a weather hardened fuse holder mounted to the firewall. I obviously installed it, just didn't remember it being there, just looked like another sensor. Opener her up and there sat a 25 amp blown fuse. Replaced it, power up the system and checked computer communications. It's alive - hooray. Used the diagnostic tool to turn on the fuel pump for a few seconds, then turned it off, went to ignition and turned the key. Started right up, wiped up the sweat. Put everything all back together.

I hate it when a hour or two job turns into multiple days. At least I doubt I will forget about that fuse again.

Removed the intake and exhaust manifold, remove all the nuts holding the exhaust system together, now just have to get the cat, muffler, and piping out so I can install the replacements. Just going stock equivalent as I'm not interested in increasing the noise level in the cabin.

Muffler and cat are original and looking pretty tired.

FAILED

Spent all day doing a three hour job and had to abort, sigh. Changed out radiator several weeks ago to address an overtemp issue, after finally getting the temp gage working. Radiator did not fix the problem. Spent today changing the water pump and thermostat and flushing the block as much as I could with a hose. Put it all back together, started right up and viola - water leaks, ugh. One hose having clamping issues and some kind of leak around the pump or thermostat housing. Couldn't tell with fan blowing everything around, so off comes the radiator shroud and fan, put belt back on and fire up. Leaking around thermostat housing, thry to tighten up, no joy. Pull housing off, clean everything up and reapply high temp sealant and gasket, put back together, fire up. leaking. Frustrated and sunburnt, so nobody can tell I'm having issues. Wife comes out regularly to see if done yet - really helps things out. Pull off housing again, however lower flange stays in-place, oh joy, overtightened flange and initially cracked, then busted housing.

Just finishing up ordering new housing gaskets, etc. Now I have to push the vehicles around so I can get the truck out and drive it until I get my parts in and the wife gives me more time to complete the repair. And I don't even know if this all resolves the heating issue.

Still cheaper then getting a new car

Dadamsnv said:

Lame!

Did the timing cover look all electrolysised away like the water pump veins were scraping away material?

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Nope. I did not think the water pump was actually bad, however it is the original pump and was the original radiator. Thermostat was replaced like 10 years ago when I did a MPI conversion. The Jeep only has about 50K miles on it since it was in storage for a little over 10 years a long time ago and my commute is 10 miles a day since the storage timeframe, so the mileage stays low. Since the radiator was 35+ years old and the brass/copper bi-metal corrosion would occur engine running or not and I could see build-up around the core tubes, it was reasonable to replace it. Since radiator shops are few and far between these days, it was easier and cost effective to just get a new aluminum radiator and be done with it. The removed water pump looked like new inside, impellers were clean and in good shape, no apparent wear, no shaft slop or anything. Will probably clean it up and keep it as an emergency backup.

I would have brushed off the overheat as an instrumentation thing, except I am periodically getting MAT over temp after long drives and a brief (15~30 mins) shutdown and drive again. On the restart the CEL comes on and the code scanner reports it as MAT, so something is happening.

Dadamsnv said:

Maybe the fan clutch quit? Maybe an exhaust leak has you running lean? I'm grasping at straws. Haha.

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Fan clutch may be week, though overtemp is both parked or driving. Bought a new clutch, however the new radiator is a three core and consumes more engine compartment space and the new clutch is about 3/8 to 1/2 in deeper and hard contacts the radiator, so have to stick with the old clutch for the time being.

Also just rebuilt the entire exhaust system a month or so ago and the last check of the computer scanner, tne engine is not running lean, though I plan on reconnecting the scanner as it can give me engine burn as well as engine temp from a separate sender, so I'm still not ruling instrumentation problems.

Just a pain to have failed so miserably.

Doing some research tonight I stumbled on a post that Haynes manuals do not always give the correct torques, then quite often just give torque values for bolt sizing, so I probably cracked the housing on initial installation and blew a whole day plus the recovery time.

I'm open to any suggestions though, always open to learning new stuff.

Just installed new (modern) accessory power. Can finally get rid of the 12V to USB adapters and the 12V accessory power splitter. Yay!